US11322083B2 - OLED display panel and driving method thereof - Google Patents

OLED display panel and driving method thereof Download PDF

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US11322083B2
US11322083B2 US16/499,286 US201916499286A US11322083B2 US 11322083 B2 US11322083 B2 US 11322083B2 US 201916499286 A US201916499286 A US 201916499286A US 11322083 B2 US11322083 B2 US 11322083B2
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pixel unit
electrically connected
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US20210335236A1 (en
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Chenglei NIE
Baixiang Han
Kun CAO
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Shenzhen China Star Optoelectronics Semiconductor Display Technology Co Ltd
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Shenzhen China Star Optoelectronics Semiconductor Display Technology Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
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    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
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    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3266—Details of drivers for scan electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3275—Details of drivers for data electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
    • G09G2300/0809—Several active elements per pixel in active matrix panels
    • G09G2300/0819—Several active elements per pixel in active matrix panels used for counteracting undesired variations, e.g. feedback or autozeroing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
    • G09G2300/0809—Several active elements per pixel in active matrix panels
    • G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
    • G09G2300/0809—Several active elements per pixel in active matrix panels
    • G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
    • G09G2300/0861—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/029—Improving the quality of display appearance by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
    • G09G2320/0295—Improving the quality of display appearance by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel by monitoring each display pixel
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G09G2320/045—Compensation of drifts in the characteristics of light emitting or modulating elements

Definitions

  • the present disclosure relates to a technical field of displays, and more particularly to an organic light emitting diode (OLED) display panel and a driving method thereof.
  • OLED organic light emitting diode
  • OLED display devices have advantages of being self-luminous, having low driving voltages, high luminous efficiency, short response time, high sharpness and contrast, nearly 180° viewing angles, and wide operating temperature ranges, and allowing implementation of flexible displays and large area full color displays, etc., and have been commonly recognized by industry as display devices with the most development potential.
  • OLED devices generally include: substrates, anodes formed on substrates, hole injection layers formed on anodes, hole transporting layers formed on hole injection layers, luminescent material layers formed on hole transporting layers, electron transporting layers formed on luminescent material layers, electron injection layers formed on electron transporting layers, and cathodes formed on electron injection layers.
  • a light emission principle of OLED devices is that semiconductor materials and organic luminescent materials are driven by electric fields, causing luminescence by carrier injection and recombination.
  • OLED devices usually use indium tin oxide (ITO) electrodes and metal electrodes to correspondingly serve as anodes and cathodes of OLED devices.
  • ITO indium tin oxide
  • Electrons and holes are correspondingly injected into electron transporting layers and hole transporting layers correspondingly from cathodes and anodes. Electrons and holes migrate to luminescent material layers correspondingly through electron transporting layers and hole transporting layers, and meet in luminescent material layers, to form excitons and excite luminescent molecules. Excited luminescent molecules emit visible light through radiation relaxation.
  • a first TFT is referred to as a switching TFT.
  • the first TFT is configured to control entry of a data signal.
  • a second TFT is referred to as a driving TFT.
  • the second TFT is configured to control a current passing through an OLED. Therefore, the importance of a threshold voltage of the driving TFT is obvious. A positive or negative drift of the threshold voltage cause different currents to flow through the OLED under the same data signal, resulting in a problem of display non-uniformity.
  • the TFT fabricated using low temperature polysilicon (LTPS) or oxide may exhibit a drift of the threshold voltage during a using process. For example, factors such as irradiation of oxide semiconductor and voltage stress effects of source and drain electrodes may cause the drift of the threshold voltage. As a result, a current flowing through the OLED is inconsistent with a required current and display uniformity of a panel is not satisfied.
  • the drift of the threshold voltage in the typical 2T1C circuit cannot be improved by regulation. Therefore, a different method needs to be used to reduce or even eliminate effects of the drift of threshold voltage.
  • An approach of implementing threshold voltage compensation for the driving TFT simply by adding new TFTs and signal lines inside a pixel is called internal compensation.
  • a compensation process is relatively simple and operation speed is faster.
  • Disadvantages of this approach are that the pixel circuit is complex, and a compensation range is limited.
  • An approach of performing threshold voltage compensation by an external driving chip of the panel is called external compensation.
  • Advantages of this approach are that the pixel circuit is relatively simple, and a compensation range is relatively large.
  • Disadvantages of this approach are that a compensation process is complex, and operation speed is slow.
  • An object of the present disclosure is to provide an organic light emitting diode (OLED) display panel that can compensate for a non-uniformity of a corresponding initial threshold voltage of each driving thin film transistor (TFT) caused by a process, and a permanent drift of a corresponding actual threshold voltage of each driving TFT due to external stress, and can instantly compensate for a relatively smaller drift of the actual threshold voltage occurred when the OLED display panel is lightened.
  • OLED organic light emitting diode
  • An object of the present disclosure is to provide an OLED display panel driving method that can compensate for a non-uniformity of a corresponding initial threshold voltage of each driving TFT caused by a process, and a permanent drift of a corresponding actual threshold voltage of each driving TFT due to external stress, and can instantly compensate for a relatively smaller drift of the actual threshold voltage occurred when the OLED display panel is lightened.
  • an OLED display panel including: a plurality of pixel unit circuits and an external compensation unit connected to all of the pixel unit circuits.
  • the external compensation unit is configured to perform external compensation on each of the pixel unit circuits, obtain an initial threshold voltage of a corresponding driving TFT of each of the pixel unit circuits, add the initial threshold voltage to a predetermined initial potential, and then input a sum of the initial threshold voltage and the predetermined initial potential to each of the pixel unit circuits.
  • Each of the pixel unit circuits is configured to perform internal compensation based on the sum of the initial threshold voltage and the predetermined initial potential, to compensate for a drift of an actual threshold voltage of the corresponding driving TFT.
  • Each of the pixel unit circuits includes: a corresponding first TFT, a corresponding second TFT, a corresponding third TFT, a corresponding fourth TFT, a corresponding fifth TFT, a corresponding sixth TFT, a corresponding capacitor, and a corresponding light emitting diode (LED).
  • a corresponding first TFT a corresponding second TFT
  • a corresponding third TFT a corresponding fourth TFT
  • a corresponding fifth TFT a corresponding sixth TFT
  • a corresponding capacitor and a corresponding light emitting diode (LED).
  • LED light emitting diode
  • the first TFT has a gate electrically connected to a first node, a source electrically connected to a second node, and a drain electrically connected to a third node, and the first TFT is the driving TFT.
  • the second TFT has a gate receiving an (n)th scan signal corresponding to a corresponding row that each of the pixel unit circuits is located, a source electrically connected to the second node, and a drain receiving a data signal.
  • the third TFT has a gate receiving the (n)th scan signal corresponding to the corresponding row that each of the pixel unit circuits is located, a source electrically connected to the first node, and a drain electrically connected to the third node.
  • the fourth TFT has a gate receiving an (n ⁇ 1)th scan signal corresponding to a previous row of the corresponding row that each of the pixel unit circuits is located, a source receiving the sum of the initial threshold voltage and the predetermined initial potential, and a drain electrically connected to the first node.
  • the fifth TFT has a gate receiving a control signal, a source receiving a positive supply voltage, and a drain electrically connected to the second node.
  • the sixth TFT has a gate receiving the control signal, a source electrically connected to the third node, and the drain electrically connected to an anode of the LED.
  • a cathode of the LED receives a negative supply voltage.
  • the capacitor has one end electrically connected to the first node, and the other end electrically connected to the positive supply voltage.
  • the first TFT, the second TFT, the third TFT, the fourth TFT, the fifth TFT, and the sixth TFT are all P-type TFTs.
  • control signal, the (n ⁇ 1)th scan signal, and the (n)th scan signal are combined such that a plurality of corresponding combined portions correspond to a reset phase, a phase for data to be input and to program, and a display light emitting phase sequentially.
  • the control signal is at a high potential
  • the (n ⁇ 1)th scan signal is at a low potential
  • the (n)th scan signal is at the high potential
  • the control signal is at the high potential
  • the (n ⁇ 1)th scan signal is the high potential
  • the (n)th scan signal is at the low potential.
  • the control signal is at the low potential
  • the (n ⁇ 1)th scan signal is at the high potential
  • the (n)th scan signal is at the high potential.
  • the present disclosure also provides an OLED display panel driving method including:
  • a step S 1 of providing an OLED display panel wherein the OLED display panel includes: a plurality of pixel unit circuits and an external compensation unit connected to all of the pixel unit circuits;
  • a step S 2 of performing external compensation on each of the pixel unit circuits obtaining an initial threshold voltage of a corresponding driving TFT of each of the pixel unit circuits, adding the initial threshold voltage to a predetermined initial potential, and then inputting a sum of the initial threshold voltage and the predetermined initial potential to each of the pixel unit circuits by the external compensation unit;
  • Each of the pixel unit circuits includes: a corresponding first TFT, a corresponding second TFT, a corresponding third TFT, a corresponding fourth TFT, a corresponding fifth TFT, a corresponding sixth TFT, a corresponding capacitor, and a corresponding LED.
  • the first TFT has a gate electrically connected to a first node, a source electrically connected to a second node, and a drain electrically connected to a third node, and the first TFT is the driving TFT.
  • the second TFT has a gate receiving an (n)th scan signal corresponding to a corresponding row that each of the pixel unit circuits is located, a source electrically connected to the second node, and a drain receiving a data signal.
  • the third TFT has a gate receiving the (n)th scan signal corresponding to the corresponding row that each of the pixel unit circuits is located, a source electrically connected to the first node, and a drain electrically connected to the third node.
  • the fourth TFT has a gate receiving an (n ⁇ 1)th scan signal corresponding to a previous row of the corresponding row that each of the pixel unit circuits is located, a source receiving the sum of the initial threshold voltage and the predetermined initial potential, and a drain electrically connected to the first node.
  • the fifth TFT has a gate receiving a control signal, a source receiving a positive supply voltage, and a drain electrically connected to the second node.
  • the sixth TFT has a gate receiving the control signal, a source electrically connected to the third node, and the drain electrically connected to an anode of the LED.
  • a cathode of the LED receives a negative supply voltage.
  • the capacitor has one end electrically connected to the first node, and the other end electrically connected to the positive supply voltage.
  • the first TFT, the second TFT, the third TFT, the fourth TFT, the fifth TFT, and the sixth TFT are all P-type TFTs.
  • control signal, the (n ⁇ 1)th scan signal, and the (n)th scan signal are combined such that a plurality of corresponding combined portions correspond to a reset phase, a phase for data to be input and to program, and a display light emitting phase sequentially.
  • the control signal is at a high potential
  • the (n ⁇ 1)th scan signal is at a low potential
  • the (n)th scan signal is at the high potential
  • the control signal is at the high potential
  • the (n ⁇ 1)th scan signal is the high potential
  • the (n)th scan signal is at the low potential.
  • the control signal is at the low potential
  • the (n ⁇ 1)th scan signal is at the high potential
  • the (n)th scan signal is at the high potential.
  • An OLED display panel of the present disclosure includes a plurality of pixel unit circuits and an external compensation unit connected to all of the pixel unit circuits.
  • the external compensation unit performs external compensation on each of the pixel unit circuits, obtains an initial threshold voltage of a corresponding driving TFT of each of the pixel unit circuits, adds the initial threshold voltage to a predetermined initial potential, and then inputs a sum of the initial threshold voltage and the predetermined initial potential to each of the pixel unit circuits.
  • Each of the pixel unit circuits performs internal compensation based on the sum of the initial threshold voltage and the predetermined initial potential. That is, the external compensation and the internal compensation are combined.
  • the external compensation can compensate for a non-uniformity of the corresponding initial threshold voltage of each driving TFT caused by a process, and a permanent drift of a corresponding actual threshold voltage of each driving TFT due to external stress.
  • the internal compensation can instantly compensate for a relatively smaller drift of the actual threshold voltage occurred when the OLED display panel is lightened.
  • An OLED display panel driving method of the present disclosure combines the external compensation and the internal compensation.
  • the external compensation can compensate for the non-uniformity of the corresponding initial threshold voltage of each driving TFT caused by the process, and the permanent drift of the corresponding actual threshold voltage of each driving TFT due to the external stress.
  • the internal compensation can instantly compensate for the relatively smaller drift of the actual threshold voltage occurred when the OLED display panel is lightened.
  • FIG. 1 is a schematic diagram of an OLED display panel of the present disclosure.
  • FIG. 2 is a schematic diagram of a pixel unit circuit of the OLED display panel of the present disclosure.
  • FIG. 3 is a timing diagram of a plurality of signals of the pixel unit circuit of the OLED display panel of the present disclosure.
  • FIG. 4 is a schematic diagram of the pixel unit circuit of the OLED display panel of the present disclosure during a reset phase.
  • FIG. 5 is a schematic diagram of the pixel unit circuit of the OLED display panel of the present disclosure during a phase for data to be input and to program.
  • FIG. 6 is a schematic diagram of the pixel unit circuit of the OLED display panel of the present disclosure during a display light emitting phase.
  • FIG. 7 is a flowchart of an OLED display panel driving method of the present disclosure.
  • an organic light emitting diode (OLED) display panel including: a plurality of pixel unit circuits 10 and an external compensation unit 20 connected to all of the pixel unit circuits 10 .
  • the external compensation unit 20 is configured to perform external compensation on each of the pixel unit circuits 10 , obtain an initial threshold voltage Vth 1 of a corresponding driving thin film transistor (TFT) of each of the pixel unit circuits 10 , add the initial threshold voltage Vth 1 to a predetermined initial potential Vi, and then input a sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi to each of the pixel unit circuits 10 .
  • TFT driving thin film transistor
  • Each of the pixel unit circuits 10 is configured to perform internal compensation based on the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi, to compensate for a drift of an actual threshold voltage Vth of the corresponding driving TFT.
  • each of the pixel unit circuits 10 includes: a corresponding first TFT T 1 , a corresponding second TFT T 2 , a corresponding third TFT T 3 , a corresponding fourth TFT T 4 , a corresponding fifth TFT T 5 , a corresponding sixth TFT T 6 , a corresponding capacitor C, and a corresponding light emitting diode (LED) D.
  • the first TFT T 1 has a gate electrically connected to a first node G, a source electrically connected to a second node S, and a drain electrically connected to a third node Q, and the first TFT T 1 is the driving TFT.
  • the second TFT T 2 has a gate receiving an (n)th scan signal Scan(n) corresponding to a corresponding row that each of the pixel unit circuits 10 is located, a source electrically connected to the second node S, and a drain receiving a data signal Vdata.
  • the third TFT T 3 has a gate receiving the (n)th scan signal Scan(n) corresponding to the corresponding row that each of the pixel unit circuits 10 is located, a source electrically connected to the first node G, and a drain electrically connected to the third node Q.
  • the fourth TFT T 4 has a gate receiving an (n ⁇ 1)th scan signal Scan(n ⁇ 1) corresponding to a previous row of the corresponding row that each of the pixel unit circuits 10 is located, a source receiving the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi, and a drain electrically connected to the first node G.
  • the fifth TFT T 5 has a gate receiving a control signal EM, a source receiving a positive supply voltage VDD, and a drain electrically connected to the second node S.
  • the sixth TFT T 6 has a gate receiving the control signal EM, a source electrically connected to the third node Q, and the drain electrically connected to an anode of the LED D.
  • a cathode of the LED D receives a negative supply voltage VSS.
  • the capacitor C has one end electrically connected to the first node G, and the other end electrically connected to the positive supply voltage VDD.
  • the first TFT T 1 , the second TFT T 2 , the third TFT T 3 , the fourth TFT T 4 , the fifth TFT T 5 , and the sixth TFT T 6 are all P-type TFTs.
  • control signal EM, the (n ⁇ 1)th scan signal Scan(n ⁇ 1), and the (n)th scan signal Scan(n) are combined such that a plurality of corresponding combined portions correspond to a reset phase P 1 , a phase for data to be input and to program P 2 , and a display light emitting phase P 3 sequentially.
  • the control signal EM is at a high potential
  • the (n ⁇ 1)th scan signal Scan(n ⁇ 1) is at a low potential
  • the (n)th scan signal Scan(n) is at the high potential.
  • the second TFT T 2 , the third TFT T 3 , the fifth TFT T 5 , and the sixth TFT T 6 are all turned off.
  • the fourth TFT T 4 is turned on.
  • a voltage at the gate of the first TFT T 1 is reset to the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi.
  • This process is for compensating for a non-uniformity of the corresponding initial threshold voltage of each driving TFT caused by a process, and a non-uniformity the corresponding threshold voltage caused by factors such as voltage stress or temperature during a previous lightening process of the OLED display panel.
  • the control signal EM is at the high potential
  • the (n ⁇ 1)th scan signal Scan(n ⁇ 1) is the high potential
  • the (n)th scan signal Scan(n) is at the low potential.
  • the fourth TFT T 4 , the fifth TFT T 5 , and the sixth TFT T 6 are all turned off.
  • the second TFT T 2 and the third TFT T 3 are turned on.
  • the data signal Vdata is input to the source of the first TFT T 1 .
  • the gate and the drain of the first TFT T 1 are connected together, so that a potential at the gate is same as a potential at the drain.
  • the gate and the drain of the first TFT T 1 start to discharge until the voltage at the gate of the first TFT T 1 is equal to Vdd+Vth.
  • the actual threshold voltage Vth of the first TFT T 1 and the data signal Vdata are held at the gate of the first TFT T 1 .
  • the control signal EM is at the low potential
  • the (n ⁇ 1)th scan signal Scan(n ⁇ 1) is at the high potential
  • the (n)th scan signal Scan(n) is at the high potential.
  • the second TFT T 2 , the third TFT T 3 , and the fourth TFT T 4 are all turned off.
  • the fifth TFT T 5 and the sixth TFT T 6 are turned on.
  • the present disclosure uses both the advantage of fast operation speed of an internal compensation circuit and the advantage of a large compensation range of an external compensation circuit.
  • An internal compensation method and an external compensation method of a pixel compensation circuit are combined. Before the OLED display panel is driven to be lightened, the external compensation is first performed by the external compensation unit 20 . The initial threshold voltage Vth 1 of the corresponding driving TFT of each of the pixel unit circuits 10 is obtained.
  • the initial threshold voltage Vth 1 is added to the predetermined initial potential Vi, and the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi is input to each of the pixel unit circuits 10 and act together with a process of the internal compensation of each of the pixel unit circuits 10 .
  • the external compensation can compensate for a non-uniformity of the corresponding initial threshold voltage Vth 1 of each driving TFT caused by a process, and a permanent drift of the corresponding actual threshold voltage Vth of each driving TFT due to external stress.
  • the internal compensation can instantly compensate for a relatively smaller drift of the actual threshold voltage Vth occurred when the OLED display panel is lightened.
  • the corresponding initial threshold voltage Vth 1 of each of the driving TFTs in the OLED display panel differs by ⁇ 1V due to process reasons, if only internal compensation is performed, a current flowing through the corresponding LED D of each of the pixel unit circuits 10 may differ by a percentage as high as around 15%. At this time, the OLED display panel exhibits a significant non-uniformity.
  • the present disclosure may control the current I OLED flowing through the corresponding LED D of each of the pixel unit circuits 10 to differ by at most 2%. At this time, uniformity performance of the panel is greatly enhanced.
  • the OLED display panel When the OLED display panel performs external compensation without internal compensation, the actual threshold voltage Vth of each of the driving TFTs drifts by ⁇ 0.5V due to temperature or voltage stress. Then, a current I OLED flowing through the corresponding LED D of each of the pixel unit circuits 10 may differ by a percentage as high as around 25%.
  • the present disclosure may control the current I OLED flowing through the corresponding LED D of each of the pixel unit circuits 10 to differ by at most 5%. At this time, uniformity performance of the panel is greatly enhanced.
  • the present disclosure also provides an OLED display panel driving method including the following steps.
  • an OLED display panel is provided.
  • the OLED display panel includes: a plurality of pixel unit circuits 10 and an external compensation unit 20 connected to all of the pixel unit circuits 10 .
  • a step S 2 external compensation are performed on each of the pixel unit circuits 10 , an initial threshold voltage Vth 1 of a corresponding driving TFT of each of the pixel unit circuits 10 is obtained, the initial threshold voltage Vth 1 is added to a predetermined initial potential Vi, and a sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi is input to each of the pixel unit circuits 10 by the external compensation unit 20 .
  • a step S 3 internal compensation is performed based on the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi by each of the pixel unit circuits 10 , to compensate for a drift of an actual threshold voltage Vth of the corresponding driving TFT.
  • each of the pixel unit circuits 10 includes: a corresponding first TFT T 1 , a corresponding second TFT T 2 , a corresponding third TFT T 3 , a corresponding fourth TFT T 4 , a corresponding fifth TFT T 5 , a corresponding sixth TFT T 6 , a corresponding capacitor C, and a corresponding LED D.
  • the first TFT T 1 has a gate electrically connected to a first node G, a source electrically connected to a second node S, and a drain electrically connected to a third node Q, and the first TFT T 1 is the driving TFT.
  • the second TFT T 2 has a gate receiving an (n)th scan signal Scan(n) corresponding to a corresponding row that each of the pixel unit circuits 10 is located, a source electrically connected to the second node S, and a drain receiving a data signal Vdata.
  • the third TFT T 3 has a gate receiving the (n)th scan signal Scan(n) corresponding to the corresponding row that each of the pixel unit circuits 10 is located, a source electrically connected to the first node G, and a drain electrically connected to the third node Q.
  • the fourth TFT T 4 has a gate receiving an (n ⁇ 1)th scan signal Scan(n ⁇ 1) corresponding to a previous row of the corresponding row that each of the pixel unit circuits 10 is located, a source receiving the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi, and a drain electrically connected to the first node G.
  • the fifth TFT T 5 has a gate receiving a control signal EM, a source receiving a positive supply voltage VDD, and a drain electrically connected to the second node S.
  • the sixth TFT T 6 has a gate receiving the control signal EM, a source electrically connected to the third node Q, and the drain electrically connected to an anode of the LED D.
  • a cathode of the LED D receives a negative supply voltage VSS.
  • the capacitor C has one end electrically connected to the first node G, and the other end electrically connected to the positive supply voltage VDD.
  • the first TFT T 1 , the second TFT T 2 , the third TFT T 3 , the fourth TFT T 4 , the fifth TFT T 5 , and the sixth TFT T 6 are all P-type TFTs.
  • the control signal EM, the (n ⁇ 1)th scan signal Scan(n ⁇ 1), and the (n)th scan signal Scan(n) are combined such that a plurality of corresponding combined portions correspond to a reset phase P 1 , a phase for data to be input and to program P 2 , and a display light emitting phase P 3 sequentially.
  • the control signal EM is at a high potential
  • the (n ⁇ 1)th scan signal Scan(n ⁇ 1) is at a low potential
  • the (n)th scan signal Scan(n) is at the high potential.
  • the second TFT T 2 , the third TFT T 3 , the fifth TFT T 5 , and the sixth TFT T 6 are all turned off.
  • the fourth TFT T 4 is turned on.
  • a voltage at the gate of the first TFT T 1 is reset to the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi.
  • This process is for compensating for a non-uniformity of the corresponding initial threshold voltage of each driving TFT caused by a process, and a non-uniformity the corresponding threshold voltage caused by factors such as voltage stress or temperature during a previous lightening process of the OLED display panel.
  • the control signal EM is at the high potential
  • the (n ⁇ 1)th scan signal Scan(n ⁇ 1) is the high potential
  • the (n)th scan signal Scan(n) is at the low potential.
  • the fourth TFT T 4 , the fifth TFT T 5 , and the sixth TFT T 6 are all turned off.
  • the second TFT T 2 and the third TFT T 3 are turned on.
  • the data signal Vdata is input to the source of the first TFT T 1 .
  • the gate and the drain of the first TFT T 1 are connected together, so that a potential at the gate is same as a potential at the drain.
  • the gate and the drain of the first TFT T 1 start to discharge until the voltage at the gate of the first TFT T 1 is equal to Vdd+Vth.
  • the actual threshold voltage Vth of the first TFT T 1 and the data signal Vdata are held at the gate of the first TFT T 1 .
  • the control signal EM is at the low potential
  • the (n ⁇ 1)th scan signal Scan(n ⁇ 1) is at the high potential
  • the (n)th scan signal Scan(n) is at the high potential.
  • the second TFT T 2 , the third TFT T 3 , and the fourth TFT T 4 are all turned off.
  • the fifth TFT T 5 and the sixth TFT T 6 are turned on.
  • the present disclosure uses both the advantage of fast operation speed of an internal compensation circuit and the advantage of a large compensation range of an external compensation circuit.
  • An internal compensation method and an external compensation method of a pixel compensation circuit are combined. Before the OLED display panel is driven to be lightened, the external compensation is first performed by the external compensation unit 20 . The initial threshold voltage Vth 1 of the corresponding driving TFT of each of the pixel unit circuits 10 is obtained.
  • the initial threshold voltage Vth 1 is added to the predetermined initial potential Vi, and the sum of the initial threshold voltage Vth 1 and the predetermined initial potential Vi is input to each of the pixel unit circuits 10 and act together with a process of the internal compensation of each of the pixel unit circuits 10 .
  • the external compensation can compensate for a non-uniformity of the corresponding initial threshold voltage Vth 1 of each driving TFT caused by a process, and a permanent drift of the corresponding actual threshold voltage Vth of each driving TFT due to external stress.
  • the internal compensation can instantly compensate for a relatively smaller drift of the actual threshold voltage Vth occurred when the OLED display panel is lightened.
  • the corresponding initial threshold voltage Vth 1 of each of the driving TFTs in the OLED display panel differs by ⁇ 1V due to process reasons, if only internal compensation is performed, a current flowing through the corresponding LED D of each of the pixel unit circuits 10 may differ by a percentage as high as around 15%. At this time, the OLED display panel exhibits a significant non-uniformity.
  • the present disclosure may control the current I OLED flowing through the corresponding LED D of each of the pixel unit circuits 10 to differ by at most 2%. At this time, uniformity performance of the panel is greatly enhanced.
  • the OLED display panel When the OLED display panel performs external compensation without internal compensation, the actual threshold voltage Vth of each of the driving TFTs drifts by ⁇ 0.5V due to temperature or voltage stress. Then, a current I OLED flowing through the corresponding LED D of each of the pixel unit circuits 10 may differ by a percentage as high as around 25%.
  • the present disclosure may control the current I OLED flowing through the corresponding LED D of each of the pixel unit circuits 10 to differ by at most 5%. At this time, uniformity performance of the panel is greatly enhanced.
  • an OLED display panel of the present disclosure includes a plurality of pixel unit circuits and an external compensation unit connected to all of the pixel unit circuits.
  • the external compensation unit performs external compensation on each of the pixel unit circuits, obtains an initial threshold voltage of a corresponding driving TFT of each of the pixel unit circuits, adds the initial threshold voltage to a predetermined initial potential, and then inputs a sum of the initial threshold voltage and the predetermined initial potential to each of the pixel unit circuits.
  • Each of the pixel unit circuits performs internal compensation based on the sum of the initial threshold voltage and the predetermined initial potential. That is, the external compensation and the internal compensation are combined.
  • the external compensation can compensate for a non-uniformity of the corresponding initial threshold voltage of each driving TFT caused by a process, and a permanent drift of a corresponding actual threshold voltage of each driving TFT due to external stress.
  • the internal compensation can instantly compensate for a relatively smaller drift of the actual threshold voltage occurred when the OLED display panel is lightened.
  • An OLED display panel driving method of the present disclosure combines the external compensation and the internal compensation.
  • the external compensation can compensate for the non-uniformity of the corresponding initial threshold voltage of each driving TFT caused by the process, and the permanent drift of the corresponding actual threshold voltage of each driving TFT due to external stress.
  • the internal compensation can instantly compensate for the relatively smaller drift of the actual threshold voltage occurred when the OLED display panel is lightened.
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